[PATCH] ext4: allow larger descriptor size

make block group descriptor larger.
Signed-off-by: Alexandre Ratchov <alexandre.ratchov@bull.net>
Signed-off-by: Dave Kleikamp <shaggy@austin.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/ext4/balloc.c

@@ -74,10 +74,12 @@ struct ext4_group_desc * ext4_get_group_desc(struct super_block * sb,
 		return NULL;
 	}
 
-	desc = (struct ext4_group_desc *) sbi->s_group_desc[group_desc]->b_data;
+	desc = (struct ext4_group_desc *)(
+		(__u8 *)sbi->s_group_desc[group_desc]->b_data +
+		offset * EXT4_DESC_SIZE(sb));
 	if (bh)
 		*bh = sbi->s_group_desc[group_desc];
-	return desc + offset;
+	return desc;
 }
 
 /**

fs/ext4/inode.c

@@ -2432,14 +2432,16 @@ static ext4_fsblk_t ext4_get_inode_block(struct super_block *sb,
 		return 0;
 	}
 
-	gdp = (struct ext4_group_desc *)bh->b_data;
+	gdp = (struct ext4_group_desc *)((__u8 *)bh->b_data +
+		desc * EXT4_DESC_SIZE(sb));
 	/*
 	 * Figure out the offset within the block group inode table
 	 */
 	offset = ((ino - 1) % EXT4_INODES_PER_GROUP(sb)) *
 		EXT4_INODE_SIZE(sb);
-	block = ext4_inode_table(gdp + desc) +
-			(offset >> EXT4_BLOCK_SIZE_BITS(sb));
+	block = ext4_inode_table(gdp) + (offset >> EXT4_BLOCK_SIZE_BITS(sb));
+
+
 
 	iloc->block_group = block_group;
 	iloc->offset = offset & (EXT4_BLOCK_SIZE(sb) - 1);

fs/ext4/super.c

@@ -1268,7 +1268,8 @@ static int ext4_check_descriptors (struct super_block * sb)
 			return 0;
 		}
 		first_block += EXT4_BLOCKS_PER_GROUP(sb);
-		gdp++;
+		gdp = (struct ext4_group_desc *)
+			((__u8 *)gdp + EXT4_DESC_SIZE(sb));
 	}
 
 	ext4_free_blocks_count_set(sbi->s_es, ext4_count_free_blocks(sb));
@@ -1619,7 +1620,18 @@ static int ext4_fill_super (struct super_block *sb, void *data, int silent)
 		       sbi->s_frag_size, blocksize);
 		goto failed_mount;
 	}
-	sbi->s_frags_per_block = 1;
+	sbi->s_desc_size = le16_to_cpu(es->s_desc_size);
+	if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_64BIT)) {
+		if (sbi->s_desc_size < EXT4_MIN_DESC_SIZE ||
+		    sbi->s_desc_size > EXT4_MAX_DESC_SIZE ||
+		    sbi->s_desc_size & (sbi->s_desc_size - 1)) {
+			printk(KERN_ERR
+			       "EXT4-fs: unsupported descriptor size %ld\n",
+			       sbi->s_desc_size);
+			goto failed_mount;
+		}
+	} else
+		sbi->s_desc_size = EXT4_MIN_DESC_SIZE;
 	sbi->s_blocks_per_group = le32_to_cpu(es->s_blocks_per_group);
 	sbi->s_frags_per_group = le32_to_cpu(es->s_frags_per_group);
 	sbi->s_inodes_per_group = le32_to_cpu(es->s_inodes_per_group);
@@ -1630,7 +1642,7 @@ static int ext4_fill_super (struct super_block *sb, void *data, int silent)
 		goto cantfind_ext4;
 	sbi->s_itb_per_group = sbi->s_inodes_per_group /
 					sbi->s_inodes_per_block;
-	sbi->s_desc_per_block = blocksize / sizeof(struct ext4_group_desc);
+	sbi->s_desc_per_block = blocksize / EXT4_DESC_SIZE(sb);
 	sbi->s_sbh = bh;
 	sbi->s_mount_state = le16_to_cpu(es->s_state);
 	sbi->s_addr_per_block_bits = log2(EXT4_ADDR_PER_BLOCK(sb));

include/linux/ext4_fs.h

@@ -142,6 +142,9 @@ struct ext4_group_desc
 /*
  * Macro-instructions used to manage group descriptors
  */
+#define EXT4_MIN_DESC_SIZE		32
+#define	EXT4_MAX_DESC_SIZE		EXT4_MIN_BLOCK_SIZE
+#define EXT4_DESC_SIZE(s)		(EXT4_SB(s)->s_desc_size)
 #ifdef __KERNEL__
 # define EXT4_BLOCKS_PER_GROUP(s)	(EXT4_SB(s)->s_blocks_per_group)
 # define EXT4_DESC_PER_BLOCK(s)		(EXT4_SB(s)->s_desc_per_block)
@@ -149,7 +152,7 @@ struct ext4_group_desc
 # define EXT4_DESC_PER_BLOCK_BITS(s)	(EXT4_SB(s)->s_desc_per_block_bits)
 #else
 # define EXT4_BLOCKS_PER_GROUP(s)	((s)->s_blocks_per_group)
-# define EXT4_DESC_PER_BLOCK(s)		(EXT4_BLOCK_SIZE(s) / sizeof (struct ext4_group_desc))
+# define EXT4_DESC_PER_BLOCK(s)		(EXT4_BLOCK_SIZE(s) / EXT4_DESC_SIZE(s))
 # define EXT4_INODES_PER_GROUP(s)	((s)->s_inodes_per_group)
 #endif
 
@@ -474,7 +477,7 @@ struct ext4_super_block {
 	 * things it doesn't understand...
 	 */
 	__le32	s_first_ino;		/* First non-reserved inode */
-	__le16   s_inode_size;		/* size of inode structure */
+	__le16  s_inode_size;		/* size of inode structure */
 	__le16	s_block_group_nr;	/* block group # of this superblock */
 	__le32	s_feature_compat;	/* compatible feature set */
 /*60*/	__le32	s_feature_incompat;	/* incompatible feature set */
@@ -500,7 +503,7 @@ struct ext4_super_block {
 	__le32	s_hash_seed[4];		/* HTREE hash seed */
 	__u8	s_def_hash_version;	/* Default hash version to use */
 	__u8	s_reserved_char_pad;
-	__u16	s_reserved_word_pad;
+	__le16  s_desc_size;		/* size of group descriptor */
 /*100*/	__le32	s_default_mount_opts;
 	__le32	s_first_meta_bg;	/* First metablock block group */
 	__le32	s_mkfs_time;		/* When the filesystem was created */

include/linux/ext4_fs_sb.h

@@ -29,6 +29,7 @@
  */
 struct ext4_sb_info {
 	unsigned long s_frag_size;	/* Size of a fragment in bytes */
+	unsigned long s_desc_size;	/* Size of a group descriptor in bytes */
 	unsigned long s_frags_per_block;/* Number of fragments per block */
 	unsigned long s_inodes_per_block;/* Number of inodes per block */
 	unsigned long s_frags_per_group;/* Number of fragments in a group */